1. Field of the Invention
This invention relates to thermoplastic olefin polymer compositions modified by any of a class of specific elastomers.
2. Background Information Including Description of Related Art
Thermoplastic olefin polymers such as crystalline isotactic propylene polymers prepared by means of Ziegler-Natta coordination catalysts have found wide acceptance in recent years in applications such as containers, pipes and various molded articles, e.g., various household articles such as kitchenware and toys, because of their cheapness and generally satisfactory combination of properties such as mechanical strength, chemical resistance and ease of processability.
In more recent years various properties of these olefin polymers, e.g., flexural strength, impact resistance, and processability, have been further improved by blending the olefin polymer with certain elastomers, the most commercially utilized of which are uncrosslinked ethylene-propylene copolymers (EPM) and crosslinked ethylene-propylene-diene copolymers (EPDM). Despite the improvement in properties effected by these blends, there exist applications of olefin polymers such as crystalline propylene polymers for which the use of alternate blending elastomers, which may result in improvements in properties such as melt flow rate, elongation at yield and at break, softness, flexibility and low temperature impact resistance, would be advantageous.
The following prior art references disclose olefin polymers containing any of various polymeric additives.
U.S. Pat. No. 3,985,826, issued Oct. 12, 1976 to Futamura, discloses as blending agents for polyolefins hydrogenated block copolymers of butadiene and isoprene containing at least five alternating blocks of polymers of the two monomers.
U.S. Pat. No. 4,880,878, issued Nov. 14, 1989 to Himes et al., teaches thermoplastic blends of a polyolefin such as polyethylene and two block polymers having the configuration A-B-A wherein the A blocks are a polymerized monoalkenyl aromatic hydrocarbon such as styrene and the B blocks are a hydrogenated polybutadiene which in one block polymer contains about 35 to 55 mol. % of polymerized butadiene units having the 1,2-microstructure and in the other block polymer contains about 18 to 34 mol. % of polymerized butadiene units with the 1,2-microstructure.
U.S. Pat. No. 4,968,747, issued Nov. 6, 1990 to Mallikarjun, discloses compatibilized thermoplastic resin compositions comprising a crystalline propylene polymer, a random styrenic copolymer comprising a polymerized dicarboxylic acid derivative, an elastomeric olefin polymer which may be an ethylene-propylene copolymer, an ethylene-propylene-diene terpolymer, or a hydrogenated monovinyl aromatic monomer/conjugated diene block copolymer, and an epoxy-containing olefinic polymer.
U.S. Pat. No. 5,023,300 issued Jun. 11, 1991 to Huff et al., teaches thermoplastic olefin alloys comprising an olefin copolymer elastomer (OCE) which may be a copolymer of ethylene and a C.sub.3 to C.sub.10 alpha-olefin such a propylene or 1-butene, a random copolymer of propylene (RCP) and another monoolefin such as ethylene, and optionally polypropylene.
U.S. Pat. No. 5,034,449, issued Jul. 23, 1991 to Mallikarjun, discloses polyblend compositions comprising an olefin polymer, e.g., a crystalline propylene polymer, a rubber modified styrenic resin, e.g., a styrene/maleic anhydride copolymer to which has been grafted an ethylene-propylene-diene monomer (EPDM) rubber or a conjugated diene rubber such as a homopolymer of butadiene, and a compatibilizer which may be a hydrogenated monovinyl aromatic monomer/conjugated diene block copolymer.